Fix to allow multiple fields to be updated.

The current "update" does not allow multiple fields to be updated. I made a slight change that now allows multiple fields update. Please review.

The SQL before fix was 
```code 
UPDATE `items` SET `name`= ?`description`= ?`code`= ?`price`= ? WHERE `id`=?;  ["Item A", "A", "A", 10, 1] 
```
The SQL after fix should be
```code
UPDATE `items` SET `name`= ?,`description`= ?,`code`= ?,`price`= ? WHERE `id`=?;  ["Item A", "A", "A", 10, 1] 
```